If your old device is an Apple using iOS 5 or later, and you have an iCloud account, you can transfer all your saved messages, email accounts, photos, notes, and other personal settings to your new iPad Air.
Connect your old Apple device to WiFi and to a power source.
Back it up to iCloud by going to Settings > iCloud > Storage & Backup and toggling iCloud Backup on. The time it takes to backup depends on how much data you have and on the speed of your internet connection.
iCloud backs up your device once a day. If it needs backing up before you transfer to your new iPad Air, tap Back Up Now in Settings > iCloud > Storage & Backup. Do not start transferring before the backup is finished.
Turn on your new iPad Air and complete the setup by selecting your language and country, and choose whether to enable Location Services. When prompted, choose your WiFi network.
Insert your new 4G SIM card that you've registered with EE.
When prompted to set up, choose Restore from iCloud Backup, tap Next, and enter your Apple ID and password.
Select the backup of your old device and tap Restore. Wait until the device has finished restoring from the backup.
When the restore process is complete, your iPhone will restart and be ready to use.
Connect your iPad Air to iTunes to sync data not contained in the backup (such as music, videos, apps, and so on). You can choose the data that are synced by clicking the syncing tabs in iTunes.